FRESH AIR FOR COMBUSTION
Provision for combustion and ventilation air must be in accordance with Section 5.3 of NFGC, Air for Combustion and Ventilation, or applicable
provisions of local building codes.
Canadian installations must be installed in accordance with NSCNGPIC and all authorities having jurisdiction.
WARNING: Be sure to provide enough fresh air for combustion. Enough air ensures proper combustion and
ASSURES THAT NO HAZARD WILL DEVELOP DUE TO LACK OF OXYGEN. Failure to follow this warning can cause a fire,
personal injury, or death.
You must provide for enough fresh air to assure proper combustion. The fire in the boiler uses oxygen. It must have a continuous supply. The air
in a house contains only enough oxygen to supply the burner for a short time. Outside air must enter the house to replace the oxygen used by the
burner. Study the following examples to determine your fresh air requirements.
CAUTION:
Air for combustion must not be contaminated by halogen compounds, which include fluoride, chloride,
bromide, and iodide. These elements are found in aerosol sprays, detergents, bleaches, cleaning solvents, salts, air
fresheners, and other household products. Excessive exposure to contaminated combustion air will result in safety and
performance related problems.
CAUTION: If a fireplace or a kitchen or bathroom exhaust fan is used, an outside air intake should be installed. These
devices rob the boiler and water heater of combustion air which can cause fire, personal injury or death.
PROCEDURE 1—BOILER LOCATED IN UNCONFINED SPACE
EXAMPLE 1:
An unconfined space is defined as a space whose volume is not less than 50 cubic feet per 1,000 Btu per hour of the total input rating of all
appliances installed in that space.
If your boiler is in an open area (unpartitioned basement) in a conventional house, the air that leaks through cracks around doors and windows
will usually be adequate to provide air for combustion. The doors should not fit tightly. Do not caulk cracks around windows.
Equipment located in buildings of unusually tight construction shall be provided with air for combustion, ventilation, and dilution of flue gases
using methods described in example 2B or shall be specially engineered. The authority having jurisdiction must approve specially engineered
installations.
Table 1—Room Large In Comparison With Boiler
BOILER SIZE
(SECTIONS)
BOILER VOLUME
(CU FT)
MINIMUM ROOM
VOLUME REQUIRED
TO BE LARGE
ROOM
(CU FT)*
3 6.3 100.4
4 8.1 129.4
5 9.9 158.4
6 11.7 187.4
7 13.5 216.4
8 15.3 245.4
9 17.2 274.5
* For room with single boiler only.
Table 2—Minimum Clearances From Combustible Materials and For Servicing
PART OF BOILER
ALCOVE OR ROOM
NOT LARGE
IN COMPARISON
WITH BOILER (IN.)
ROOM LARGE
IN COMPARISON
WITH BOILER (IN.)
Top 66
Rear 66
Control Side 76
Opposite Control Side 66
Front 18 18
Flue/Vent Connector 66
Boiler Piping 11
—5—
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